That device list suggests that you require cellular access. Does the user in question have a wifi only iPad? The dialogue would be shown if the app required capabilities that the device did not have.
There is no change to the App Store policy - iPad users can still download iPhone apps, and it's pretty clear in the store that you're not getting an iPad-native version.
To answer your second question, the information shown in the App Store comes from what is set in your info plist- the minimum targeted version of iOS, and then device capabilities. Device capabilities are explained here.